# Connection wish fulfillment
# for wishes of the form:
# "Wish $tag is connected to $tag2" or "Wish $tag is dynamically connected to $tag2"

When /anyone/ wishes /source/ is connected to /sink/ & \
  /source/ has region /source_region/ & \
  /sink/ has region /sink_region/ {

   if {$source == $sink} {return}

   set source [region centroid $source_region]
   set sink [region centroid $sink_region]

   set direction [vec2 sub $sink $source]

   set c [vec2 scale [vec2 add $source $sink] 0.5]
   set angle [expr {atan2(-[lindex $direction 1], [lindex $direction 0]) - 3.14159/2}]

   set color grey
   Wish to draw a stroke with points [list $source $sink] width 2 color $color
   Wish to draw a shape with sides 3 center $c radius 30 radians $angle color $color filled true
}

set speed 75
set spacing 50
set maxsize 25

When /anyone/ wishes /source/ is dynamically connected to /sink/ & \
  /source/ has region /source_region/ & \
  /sink/ has region /sink_region/ {

   if {$source == $sink} {return}

   set source [region centroid $source_region]
   set sink [region centroid $sink_region]

   set direction [vec2 normalize [vec2 sub $sink $source]]
   set distance [vec2 distance $sink $source]
   set angle [expr {atan2(-[lindex $direction 1], [lindex $direction 0]) - 3.14159/2}] 

   lassign [vec2 scale [vec2 add $source $sink] 0.5] cx cy

   Wish to draw a stroke with points [list $source $sink] width 1 color white
   
   
   When the clock time is /t/ {
     set offset [expr {round($t*$speed) % $spacing}]
     set count [expr {round($distance / $spacing)}]

     for {set p $offset} {$p < $distance} {incr p $spacing} {
        set c [vec2 add $source [vec2 scale $direction $p]]
        set s [expr {min($maxsize, 0.20*min($p, $distance - $p))}]
        Wish to draw a shape with sides 3 center $c radius $s radians $angle color white filled true
      }
    }
}